A variety of studies have heretofore been made on color photographic materials in order to improve the image-producing characteristics including the color reproductivity and the graininess and to intensify the sensitivity. One study involves the development of compounds that can release a photographically useful group by the reaction with an oxidized form of a developing agent. Typical examples of such compounds are couplers for releasing a development inhibitor (DIR couplers), couplers for releasing a dye (colored couplers), etc. The fundamental functions of these couplers are described in, for example, Photographic Science and Engineering, Vol. 13, pages 74 and 214 (1969) and PSA Journals, Vol. 13, page 94 (1947).
As taught in the above-cited publications, the conventional compounds which have the property of improving the image characteristics react with an oxidized form of a developing agent to release a photographically useful group. Specifically, a chemical reaction occurs in the compound corresponding to the image of the exposed silver halide in the photographic light-sensitive materials, whereby a development inhibitor is formed in the compound or a dye is released therefrom.
However, such compounds have been desired as generate the chemical reaction countercorresponding to the image of the exposed silver halide. A complete solution of the various problems which heretofore have not been completely solved is expected by the development of such compounds. For instance, the release of a development inhibitor from the compound countercorresponding to the image of the exposed silver halide will be effective for the reduction of the increase in fog which is often troublesome in the use of a high speed coupler. This is because no development inhibitor is released in the image part and, therefore, the fog in the non-exposed part can be reduced without lowering the color density in the image part.
In the azo dyes which are temporarily short-waved because of a group linked with the auxochrome of the dye, the cleavage of the linked group countercorresponding to the image of the exposed silver halide for color reproduction, if possible, will be effective for using the dyes as a masking agent which is preferable to the conventional masking agents. The conventional masking method using general colored couplers is accompanied by a decrease in sensitivity, which is caused by the addition of a colored compound to a light-sensitive layer. For instance, a magenta-colored cyan coupler is generally added to a red-sensitive layer so as to compensate for the side-absorption of green light by the colored dye from a cyan coupler. In this example, however, the red-sensitive layer should lack the amount of light in the side of the short wavelength because of the absorption of light in the side of the long wavelength by the magenta-colored cyan coupler used. In particular, when phenol type cyan couplers, as illustrated, e.g., in U.S. Pat. Nos. 4,333,999 and 4,451,559, are used as the cyan coupler, the use of the magenta-colored cyan coupler is essential since the colored dye formed from the couplers have noticeable side-absorption as mentioned above and, thus, the decrease in sensitivity of the red-sensitive layer is extreme.
For the same reason as above, the use of a yellow-colored magenta coupler in a green-sensitive layer results in an insufficient amount of light in the side of the short wavelength for the green-sensitive layer and, as a result, a decrease in sensitivity of the green-sensitive layer occurs. One method for solving the above problem, as described in U.S. Pat. No. 4,427,763, involved temporarily short-waving a colored coupler by blocking the auxochrome of the coupler with an alkali-hydrolyzable group. Further, U.S. Pat. No. 4,555,477 has proposes couplers which are able to release a ligand. However, with such couplers, the coloring speed of the couplers themselves is insufficient and, therefore, they cannot be satisfactorily employed to solve the outstanding problems.
The necessity for the generation of a chemical reaction countercorresponding to the image of the exposed silver halide in the compounds to be incorporated into the photographic materials is understood from the above explanation. In this connection, some compounds which generate a chemical reaction countercorresponding to the image of an exposed silver halide (hereinafter referred to as "positive responsive compounds") have been proposed in the field of a diffusion transfer color photography. For instance, some positive-forming compounds are described in U.S. Pat. Nos. 4,199,354, 3,980,479, 4,139,379 and 4,278,598. These compounds are immobile or photographically inactive but can release a mobile and photographically useful group by an intramolecular nucleophilic substitution reaction or intramolecular electron transfer reaction. These known compounds have some efficiency in diffusion transfer color photographic materials. However, when these compounds are used in coupler-containing color photographic materials as an image-forming agent, they are insufficient in the reaction speed and are almost functionless. Accordingly, positive responsive compounds that are functional with a desired reaction speed to the speed of the coupling reaction between a general coupler and the oxidized form of a general developing agent are desired in the art.